CLUSTER AND LIGAND EFFECTS IN NICKEL TIN AND RHODIUM TIN SYSTEMS

Physico-chemical properties of Ni-Sn and Rh-Sn bimetallic systems supp orted on SiO2 are studied using XRD, electron microscopy, IR-spectrosc opy of surface species, and measurements of H-2, O2, and CO adsorption . Catalytic properties of the samples are investigated in the structur e-sensitive reaction of n-hexane hydrogenolysis and in the structure-i nsensitive reaction of benzene hydrogenation. The specific catalytic a ctivity per one active surface site in the reaction of benzene hydroge nation is not affected by variation of the composition of the nickel-t in catalyst. An increase in the activity for the Rh-Sn system is obser ved in comparison with Rh/SiO2 within the range of Sn contents from 0 to 2.3 wt %. A synergistic effect is observed for both systems in n-he xane hydrogenolysis upon variation of the alloy composition. The resul ts obtained are interpreted in terms of ligand and cluster effects exh ibited upon alloying of the metals.